1. Field of the Invention
This invention relates to color television camera apparatus and color television signal generating methods.
2. Description of the Prior Art
In a solid-state imaging device comprising a solid-state image sensor having a discrete pixel structure, including for example charge-coupled devices (CCDs), used as image pick-up means, since the solid-state image sensor itself represents a sampling system, aliasing components from spatial sampling frequencies fs are mixed into image pick-up output signals of the solid-state image sensor.
In a color television camera device, known arrangements for generating a color image include a two CCD type solid-state image pick-up device for forming three color images with a solid-state image sensor forming a green color image and a solid-state image sensor with a color coding filter forming red color pixels and blue color pixels of a color image, and a three CCD type solid-state image pick-up device forming three color images by separate solid-state image sensors.
There is also known a so-called spatial pixel shifting method, in which, to improve the resolution in the above-mentioned multiple CCD imaging devices, the solid-state image sensor for forming a red color image and the solid-state image sensor for forming a blue color image are shifted with respect to the solid-state imaging device for forming a green color image by one-half the pixel sampling period. With this spatial pixel shifting method, it becomes possible with an analog output multiple CCD imaging device to realize high resolution exceeding the upper limit imposed by the number of pixels of the solid-state image sensors.
On the other hand, in a color television camera device for digitally processing image pick-up output signals, digital signal processing is effected using a clock rate equal to approximately four times the color sub-carrier frequency f.sub.SC. In this case, the output bandwidth of composite video signals CS, produced on mixing luminance signals Y with modulated chrominance signals MOD.C, is limited to less than 2fs, for preventing the composite video signals from being affected by high harmonics of the color sub-carrier frequency f.sub.SC. In general, a clock rate equal to four times the color sub-carrier frequency f.sub.SC, is adopted in a color television camera device of the NTSC system, while a clock rate fs equal to 908 or 944 times the horizontal scanning frequency f.sub.H of the PAL system, is used in a color television camera device of the PAL system.
Meanwhile, to improve television picture quality, attempts are being made to increase the bandwidth range of television signals. However, With a color television camera device for digitally processing the image pick-up output signals from a solid state image sensor having a discrete pixel structure, such as CCDs, as described above, if the output bandwidth of the composite video signals is increased to more than 2fs, color signal components may be suppressed unnecessarily, or distortion due to higher harmonics may be produced in the color sub-carrier signals, thereby deteriorating the picture quality.
On the other hand, with a color television device for digitally processing image output signals, as described above, where the clock rate fs is equal to 4f.sub.sc in the NTSC system, or the clock rate fs is equal to 908f.sub.H or 944f.sub.H in the PAL system it is necessary to construct the digital signal processor differently, depending on the television system and hence the clock rate.